1. Field of the Invention
The present invention relates to an image processing apparatus for digitally processing an input image.
2. Related Background Art
Recently, a digital color copying machine which color-separates a color original, reads it in units of pixels, digitally processes the read image data, and outputs the processed data to a color printer to obtain a digital color hard copy has become widespread (FIG. 1A). In addition, in order to satisfy a requirement for higher speeds there is proposed a system which comprises four drums and in which images of respective colors are printed in units of drums and output from an LBP (Laser Beam Printer), as shown in FIG. 1B.
On the other hand, a demand has increasingly arisen for a system capable of printing a color reflecting original such that characters look more like characters and natural (e.g., photographic) images look more like natural images. To satisfy this demand, there is proposed a technique of separating a character portion from an image portion by image area separation. In this method, high-resolution processing is performed for the character portion such that especially black characters are printed out in black monochrome, whereas high-gradation processing is performed for the image portion. (U.S. patent application Ser. No. 173,654, U.S. Pat. No. 4,958,219, and U.S. patent application Ser. Nos. 327,098, 367,673, 519,500, 519,448, and 519,447.)
In the above color copying machine comprising four drums, a memory for storing image data is an essential part, and the image data must be compressed before it is stored if cost and transmission rate are taken into consideration.
However, there exists no conventional system in which image area judgment is performed in a system for compressing and storing image data in a memory and image processing is performed on the basis of the judgment result.
In addition, in order to realize the above operation by using a system of the conventional techniques, an operator must perform area designation for a character portion, especially, a black character portion by using a digitizer or the like so that only the designated portion is subjected to high-resolution processing in black monochrome and output.